Neurotransmitters

The Neuron and Its Function

  • Resting Potential:

    • Neurons have a resting electrical charge of approximately -70 millivolts (mV).

    • This negative charge indicates that there are more negative ions inside the neuron compared to outside.

  • Action Potential:

    • When a neuron is triggered, an action potential occurs, which is an electrical charge that travels along the axon.

    • The speed of this action potential is influenced by:

      • Axon Size: Larger diameter axons conduct impulses faster.

      • Myelin Sheath Thickness: Thicker myelin increases conduction speed by insulating the axon.

Neurotransmitters and Their Role

  • Reuptake Process:

    • Understanding reuptake is crucial for developing medications for psychological disorders.

    • Selective serotonin reuptake inhibitors (SSRIs) help maintain serotonin levels in the synapses, alleviating symptoms of depression.

  • Impact of Neurotransmitter Imbalances:

    • Deficiencies or excesses of neurotransmitters can lead to behavioral disorders.

    • Over 100 chemicals have been identified as neurotransmitters, with more anticipated to be discovered.

Major Neurotransmitters

  • Acetylcholine (ACh):

    • Common neurotransmitter involved in all physical movements by transmitting messages to skeletal muscles.

    • Plays a role in memory; reduced levels are associated with Alzheimer's disease.

  • Glutamate:

    • Major excitatory neurotransmitter, crucial for memory formation.

    • Involved in biochemical changes at synapses related to memory.

  • Gamma-Aminobutyric Acid (GABA):

    • The principal inhibitory neurotransmitter in the brain and spinal cord, moderating neuronal excitability.

  • Dopamine:

    • Involved in movement, attention, and learning.

    • Low levels are linked to Parkinson's disease; treatments aim to enhance dopamine production.

  • Endorphins:

    • Produce pain relief and mood enhancement, structurally similar to morphine.

    • Elicit feelings of euphoria, such as the "runner's high."

    • Opioids and heroin trigger endorphin release, leading to addiction risks due to their intense euphoric effects.

Basic Elements of the Nervous System

  • Neurons:

    • Fundamental units of the nervous system responsible for transmitting nerve impulses.

    • Information travels from:

      • Dendrites: Receive messages.

      • Cell Body: Processes information.

      • Axon: Extends to transmit the pulse.

Communication in the Nervous System

  • Myelin Sheath:

    • Axons are often insulated with a myelin sheath, which enhances transmission speed.

  • Action Potential Activation:

    • Upon receiving a stimulating message, a neuron generates an action potential, traveling through its axon.

    • Neurons adhere to an all-or-none law, meaning they either rest or fire, with no partial firing.